Thermomechanics of Nanocrystalline Nickel Under High Pressure-Temperature Conditions

Zhao Y, Zhang J, Clausen, B., Shen, T.D., Gray III, G.T., Wang, L.

Comparative in-situ deformation studies were conducted on nanocrystalline and bulk nickels using synchrotron x-rays at high pressures (P) and temperatures (T). We derived high-P triaxial compression yield strength as a function of temperature, which provides a new dimension to gain a thorough insight into the mechanical behaviors of materials. Contrary to tensile experiments of uniaxial loading, we observed significant work-hardening for the nano-Ni in high-pressure plastic deformation stage, whereas the micron-Ni experiences minor high-pressure work-softening and considerable energy dissipation into heat.








The significantly reduced energy dissipation for the nano-Ni during the loading-unloading cycle indicates that the nanostructured materials can endure much greater mechanical fatigue in cyclic loadings. We also correlated the yielding with the nucleation, propagation, and storage of dislocations for plastically deforming nanocrystalline materials under triaxial loading and their variations with temperature. This is particularly important in research of nano-scale materials, as differences in specific defect concentration and/or distribution can greatly alter the point at which the material yields.

This research was partially supported by COMPRES, EAR 10-43050

Zhao Y, Zhang J, Clausen, B., Shen, T.D., Gray III, G.T., Wang, L. (2007) Nano Letters Vol. 7, 426-432.


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